Interleukin-17 (IL-17) is a T-cell derived pro-inflammatory molecule that stimulates epithelial, endothelial and fibroblastic cells to produce other inflammatory cytokines and chemokines including IL-6, IL-8, G-CSF, and MCP-1 [see, Yao, Z. et al., J. Immunol., 122(12):5483-5486 (1995); Yao, Z. et al, Immunity, 3(6):811-821 (1995); Fossiez, F., et al., J. Exp. Med., 183(6): 2593-2603 (1996); Kennedy, J., et al., J. Interferon Cytokine Res., 16(8):611-7 (1996); Cai, X. Y., et al., Immunol. Lett, 62(1):51-8 (1998); Jovanovic, D. V., et al., J. Immunol., 160(7):3513-21 (1998); Laan, M., et al., J. Immunol., 162(4):2347-52 (1999); Linden, A., et al., Eur Respir J, 15(5):973-7 (2000); and Aggarwal, S. and Gurney, A. L., J Leukoc Biol. 71(1):1-8 (2002)]. IL-17 also synergizes with other cytokines including TNF-α and IL-1β to further induce chemokine expression (Chabaud, M., et al., J. Immunol. 161(1):409-14 (1998)). Interleukin 17 (IL-17) exhibits pleitropic biological activities on various types of cells. IL-17 also has the ability to induce ICAM-1 surface expression, proliferation of T cells, and growth and differentiation of CD34+ human progenitors into neutrophils. IL-17 has also been implicated in bone metabolism, and has been suggested to play an important role in pathological conditions characterized by the presence of activated T cells and TNF-α production such as rheumatoid arthritis and loosening of bone implants (Van Bezooijen et al., J. Bone Miner. Res., 14: 1513-1521 [1999]). Activated T cells of synovial tissue derived from rheumatoid arthritis patients were found to secrete higher amounts of IL-17 than those derived from normal individuals or osteoarthritis patients (Chabaud et al., Arthritis Rheum., 42: 963-970 [1999]). It was suggested that this proinflammatory cytokine actively contributes to synovial inflammation in rheumatoid arthritis. Apart from its proinflammatory role, IL-17 seems to contribute to the pathology of rheumatoid arthritis by yet another mechanism. For example, IL-17 has been shown to induce the expression of osteoclast differentiation factor (ODF) mRNA in osteoblasts (Kotake et al., J. Clin. Invest., 103: 1345-1352 [1999]). ODF stimulates differentiation of progenitor cells into osteoclasts, the cells involved in bone resorption. Since the level of IL-17 is significantly increased in synovial fluid of rheumatoid arthritis patients, it appears that IL-17 induced osteoclast formation plays a crucial role in bone resorption in rheumatoid arthritis. IL-17 is also believed to play a key role in certain other autoimmune disorders such as multiple sclerosis (Matusevicius et al., Mult. Scler., 5: 101-104 (1999); Kurasawa, K., et al., Arthritis Rheu 43(11):2455-63 (2000)) and psoriasis (Teunissen, M. B., et al., J Invest Dermatol 111(4):645-9 (1998); Albanesi, C., et al., J Invest Dermatol 115(1):81-7 (2000); and Homey, B., et al., J. Immunol. 164(12:6621-32 (2000)).
IL-17 has further been shown, by intracellular signalling, to stimulate Ca2+ influx and a reduction in [cAMP]i in human macrophages (Jovanovic et al, J. Immunol., 160:3513 [1998]). Fibroblasts treated with IL-17 induce the activation of NF-κB, [Yao et al., Immunity, 3:811 (1995), Jovanovic et al., supra], while macrophages treated with it activate NF-κB and mitogen-activated protein kinases (Shalom-Barek et al, J. Biol. Chem., 273:27467 [1998]). Additionally, IL-17 also shares sequence similarity with mammalian cytokine-like factor 7 that is involved in bone and cartilage growth. Other proteins with which IL-17 polypeptides share sequence similarity are human embryo-derived interleukin-related factor (EDIRF) and interleukin-20.
Consistent with IL-17's wide-range of effects, the cell surface receptor for IL-17 has been found to be widely expressed in many tissues and cell types (Yao et al., Cytokine, 2:794 [1997]). While the amino acid sequence of the human IL-17 receptor (IL-R) (866 amino acids) predicts a protein with a single transmembrane domain and a long, 525 amino acid intracellular domain, the receptor sequence is unique and is not similar to that of any of the receptors from the cytokine/growth factor receptor family. This coupled with the lack of similarity of IL-17 itself to other known proteins indicates that IL-17 and its receptor may be part of a novel family of signaling proteins and receptors. It has been demonstrated that IL-17 activity is mediated through binding to its unique cell surface receptor (designated herein as human IL-17R), wherein previous studies have shown that contacting T cells with a soluble form of the IL-17 receptor polypeptide inhibited T cell proliferation and IL-2 production induced by PHA, concanavalin A and anti-TCR monoclonal antibody (Yao et al., J. Immunol., 155:5483-5486 [1995]). As such, there is significant interest in identifying and characterizing novel polypeptides having homology to the known cytokine receptors, specifically IL-17 receptors.
Interleukin 17 is now recognized as the prototype member of an emerging family of cytokines. The large scale sequencing of the human and other vertebrate genomes has revealed the presence of additional genes encoding proteins clearly related to IL-17, thus defining a new family of cytokines. There are at least 6 members of the IL-17 family in humans and mice including IL-17B, IL-17C, IL-17D, IL-17E and IL-17F as well as novel receptors IL-17RH1, IL-17RH2, IL-17RH3 and IL-17RH4 (see WO 01/46420 published Jun. 28, 2001). One such IL-17 member (designated as IL-17F) has been demonstrated to bind to the human IL-17 receptor (IL-17R) (Yao et al., Cytokine, 9(11):794-800 (1997)). Initial characterization suggests that, like IL-17, several of these newly identified molecules have the ability to modulate immune function. The potent inflammatory actions that have been identified for several of these factors and the emerging associations with major human diseases suggest that these proteins may have significant roles in inflammatory processes and may offer opportunities for therapeutic intervention.
The gene encoding human IL-17F is located adjacent to IL-17 (Hymowitz, S. G., et al., Embo J, 20(19):5332-41 (2001)). IL-17 and IL-17F share 44% amino acid identity whereas the other members of the IL-17 family share a more limited 15-27% amino acid identity suggesting that IL-17 and IL-17F form a distinct subgroup within the IL-17 family (Starnes, T., et al., J Immunol. 167(8):4137-40 (2001); Aggarwal, S. and Gurney, A. L., J. Leukoc Biol, 71(1):1-8 (2002)). IL-17F appears to have similar biological actions as IL-17, and is able to promote the production of IL-6, IL-8, and G-CSF from a wide variety of cells. Similar to IL-17, it is able to induce cartilage matrix release and inhibit new cartilage matrix synthesis (see U.S.-2002-0177188-A1 published Nov. 28, 2002). Thus, like IL-17, IL-17F may potentially contribute to the pathology of inflammatory disorders. Recently, these authors have observed that both IL-17 and IL-17F are induced in T cells by the action of interleukin 23 (IL-23) (Aggarwal, S., et al., J. Biol. Chem., 278(3):1910-4 (2003)). The observation that IL-17 and IL-17F share similar chromosomal localization and significant sequence similarity sd well as the observation that IL-17 and IL-17F appear to be induced with the same cell population in response to a specific stimuli has lead to the identification of a new human cytokine that is comprised of a covalent heterodimer of IL-17 and IL-17F (herein designated IL-17A/F).
IL-17A and IL-17F are now recognized as major proinflammatory cytokines secreted by Th17T cell subset. They target almost all cell types in body and induce inflammation and tissue damage.
Human IL-17A/F is a distinctly new cytokine, distinguishable from human IL-17 and IL-17F in both protein structure and in cell-based activity assays. Through the use of purified recombinant human IL-17A/F as a standard, a human IL-17A/F-specific ELISA has been developed. Through the use of this specific ELISA, the induced expression of human IL-17A/F was detected, confirming that IL-17A/F is naturally produced from activated human T cells in culture. Hence, IL-17A/F is a distinctly new cytokine, detectable as a natural product of isolated activated human T cells, whose recombinant form has been characterized, in both protein structure and cell-based assays, as to be different and distinguishable from related cytokines.
IL-17A/F is disclosed in U.S. Application Publication Nos. 20060270003, published Nov. 30, 2006, and 20070160576, published Jul. 12, 2007. IL-17A/F has been described to as a target for treating various immune-mediated diseases (Chang and Dong, Cell Res. 17(5):435-40 (2007)); an IL-17A/F protein produced by mouse Th17 cells has been shown to induce airway neutrophil recruitment and thus having an in vivo function in airway neutrophilia (Liang et al., J Immunol 179(11):7791-9 (2007)); and the human IL-17A/F heterodimeric cytokine has been reported to signal through the IL-17RA/IL-17RC receptor complex (Wright et al., J Immunol 181(4):2799-805 (2008)).
In view of the proinflammatory properties of both IL-17A and IL-17F, it would be desirable to generate cross-reactive and bispecific antibodies that can block both IL-17A and IL-17F with high potency. Such cross-reactive and bispecific antibodies provide new therapeutic opportunities in the treatment of inflammatory and immune-related diseases, including autoimmune diseases, and in the treatment of cancer.